1. Field of the Invention
The invention relates to a fuel cell, a fuel cell stack, and a method of producing the fuel cell stack (an assembly method of assembling the fuel cell stack with good accuracy).
2. Description of the Related Art
Japanese Patent No. 3427915 (JP-B-3427915) describes an assembly method in which a plurality of holes that serve as positioning references are formed in the surface of constituent members of the fuel cell and adhesive sheets (seal plates). The fuel cell and the fuel cell stack are assembled by inserting positioning knock pins into the holes to appropriately position the fuel cell constituent members.
However, the positioning method for a fuel cell and a fuel cell stack described in Japanese Patent No. 3427915 (JP-B-3427915) has the following problems.
When assembling the stack, positioning shafts (hereinafter, referred to as “shafts”) are inserted into the positioning reference holes. If the space between the shafts and the positioning reference holes is small, the assembly accuracy becomes better; however, various problems occur. For example, it becomes difficult to insert the shafts during the assembly of unit fuel cells and during the assembling the fuel cell stack. Furthermore, if a plurality of inter-hole distances of a plurality of constituent members vary by an amount greater than or equal to a predetermined clearance, one or more of the constituent members, the adhesive sheets, etc., become misaligned and protrudes from the stack. Therefore, it becomes difficult to assemble a unit fuel cell and package unit fuel cells into a fuel cell stack, or it becomes difficult to pull out a shaft because when the shaft is to be pulled out after the packaging into a stack, a separator or the like deforms at a portion that contacts the shaft, or the like.